Method of beneficiating sand



Nov. 6, 1956 o. R. BROWN 2,769,540

METHOD oF BENEFICIATING SAND Filed Nov. 8, 1952 Miam/wmv 5Fl/UIA United States Patent O METHOD or BENEFICIATING SAND Otto R. Brown, Sacramento, Calif., assignor to American Cyanamid Company, New York, N. Y., a corporation of Maine Application November 8, 1952, Serial No. 319,510

4 Claims. (Cl. 209-166) The present invention relates to an improved process for purifying industrial sands and particularly, glass sands, by froth flotation.

Such sands generally contain ferruginous impurities in the form of iron-bearing and iron-stain minerals which are detrimental in glass making. Although such ferruginous impurities exist in the sands in a very small quantity, it is essential that they be reduced to very low limits.

There are large natural deposits of sand in the United States which have a high alumina content, and it is an advantage of my process that the alumina content of the puried glass sand may be regulated to any desired amount. The alumina constituent of industrial sand is generally present as feldspar, and the proportion of feldspar to quartz will vary widely depending upon the origin, location, and age of the deposit. A representative deposit amenable to the process of the present invention might analyze as much as 53% teldspar and 45% quartz. An assay of this product would show about 0.15% Fe203 and 11.4% A1203. The feldspar constituent would assay 21.5% A1203 and 0.1% FezOs.

During World War II and the years immediately thereafter, the glass manufacturers were able to sell glass containers, regardless of color and other defects, simply due to demand caused by tin and steel shortages during the war; that is, tin and steel shortages made it possible to sell any glass container that did not fall apart, regardless of its color. This had created a demand for highaluminous sand because of its low cost and availability; however, the high alumina content and relatively high iron content was.a disadvantage for the average glass manufacturer. The low cost of this raw material was outweighed by the diilculties incident to handling in the plant and by defective and poorly-colored containers.

With postwar competition, the glass manufacturers began to reduce the alumina content of the glass mix to around 3.5% A1203 which made it necessary for them to use a large percent of high-Silica, alumina-free sand. The present invention is the result of my discovery that by means of a two-step flotation process, ferruginous impurities can be removed from raw sand deposits and the tailing from the iron float converted into a tailor-made product by removing any undesired feldspar in a second otation step. Some feldspar may be desired in glass sands, since the sodium, potassium or calcium content of the feldspar replaces the more expensive soda ash and lime in the glass mix.

My process is very exible in that it may be used to produce a quartz concentrate, a feldspar concentrate, or any mixture of the two. By this invention, it is economically possible not only to obtain recoveries in the form of linished tailor-made concentrates considerably exceeding the recoveries obtained by prior methods of flotation, but the linished concentrates are of improved grade because of more thorough separation of the impurities in the raw sand.

My invention can best be explained by an example of a pilot plant operation on a scale comparable to a rice commercial operation. The raw sand in this example is supplied at an average rate of about 50 tons per hour. Referring to the drawing, the feed is first sized on a /e Screen with the oversize going to waste. The screened sand is scrubbed violently at about 80% solids and the discharge from the scrubber is diluted to 20% solids with water which may contain hydrouoric acid. The diluted scrubbed sand is passed over a ZO-mesh screen and the undersize material is deslimed, and dewatered in a screw classifier to approximately solids. The etlluent water and slimes from the classifier, as well as the oversize from the 20-mesh screen are sent to waste.

The sized and scrubbed sand is conditioned at high solids with about 0.45 lb./ton sulfuric acid, 0.40 lb./ton fuel oil, 0.55 lb./ton of a water-soluble petroleum sulfonate, 0.45 1b./ ton of an oil-soluble petroleum sulfonate, and about 0.01 lb./ton of pine oil. The pH of the conditioned sand is approximately 2.5, depending on the alkaline material present in the feed. The conditioned sand is diluted with water to about 25% solids and separated mechanically into at least two parts. This mechanical separation may be made either before or after the iron flotation step. The iron concentration may now readily be oated off in separate otation cells and the iron-oat tailings recovered in better than 95% yield. The iron assay of these tailings is approximately 0.06%.

A portion of the iron float tailings is dewatered to solids and the excess water returned to the conditioned ore prior to iron llotation. The dewatered tailings are conditioned with about l lb./ton hydrofluoric acid, 0.35 lb./ ton of a high molecular weight aliphatic amine acetate, 0.5 1b./ton kerosene, and 0.2 lb./ton pine oil. The pH of the conditioned material was approximately 2.8. This hydrotluoric acid-treated iron tailing was diluted with water to about 35% solids and floated to separate the quartz from the feldspar. The feldspar-bearing froth, or concentrate, is dewatered to give a high quality product having the following assay:

Feldspar concentrate and the effluent water which contains hydrouoric acid returned to the scrubber or scrubber discharge.

The quartz tailings from the feldspar oat have the following assay:

Quartz concentrate Percent SiO2 99.07 A1203 0.56 Fe2O3 0.019 CaO 0.03

The quartz tailings are intimately mixed with the tailing from the iron lloat and dewatered to give a high quality glass sand.V Again, the acid-containing water from the glass sand may be returned to the scrubber eiuent.

It will be evident from considering the process outlined above with reference to the drawing, that the quantity of iron-floated tailings which is subjected to the feldspar-float may be varied widely between 0% and 100% of the total iron tailing. The exact proportion of the raw feed which is subjected to the spar flotation will depend on the amount of feldspar in the original ore and the amount of feldspar desired in the inished glass sand. The feldspar by-product from my process has a stable market at a profitable price.

lIn the 'example described above, petroleum sulfonates Were.used..as. the iron dotation reagent. The petroleum sulfonates are a class of anionic flotation reagents obtained by the treatment of various petroleum lubricating oil ifractionsV .with V.sulfuric acid, chlorosulfoni'c acid, or

othenisulfonating agents. The petroleum ksulfonatesware* in the main mixtureszof lindeterminate compositions and it fis @probable that they 'contain aconsiderable proportion of'ihydroc'arbon sulfatos rather thantrue sulfonates; However, Vit is customary in; the industry to refer to these productsas petroleum sulfonates and 'the general class'mzty be-*further sub-dividedinto oil-soluble petroleum `sulfonates and water-soluble petroleum sulfonates, these terms vbeing:descriptive-'of the .solubility/of the two fractions. Either "oil-soluble petroleum sulfonates 0r Water-soluble petroleum'sulfonates -or mixtures thereof may be fused i1 vconditioningthen-aw sand prior 'to iron flotation, but .itiwill'berecognized 'that the quantity of .flotation/reagent addedfwilllb'e ldependent to some extent upon the .nature'fof'the'vpetroleumisulfonate and the com- Y position v.of the sand treated; Y It should` be particularly .noted that after a portion of the iron-float Vtailings `has lbeengsubj'ected Vtoi a secondy flotationffor'the purpose of separating quartzand feldspar, the excess water from boththe feldspar concentrate and the fquartztailing lis .returned tothe system, either before the scrubber'orto the lscrubber:discharge ahead of/clajssi` tication.r This of Vcourse,freduces the cost of my process,` since'it results in .atconside'rable-savingin'water.

important,however, I :have discovered that the addition More of--water containinghydrfofluoric `acidto the scrubber efuent actually'improvessthe separation of iron by ota# tion. l This'wasparticularly surprising invi'ew of the -Well-I known fact thatV iron-bearing impurities VWill not oat 'in the .presence of hydrouoric Iacid.

In the above' example,`operating With-raw sand ana` 'iyzing 0.15%' Fegoyandiruriano at ra rare of so tonsperf'hour, the mechanical splitter was adjusted lto send 26.2 'tons :perhourto the feldspar dotation 'section of theV circuit yand 21.3 tons per hour to the glass' sand mix;` With thisdistribution of the iron oatltailings,

. the glass sand product analyzed 7.90% A1203 and 0.051% f FezOa. i Y

I claim: 1. Amethod of preparing a glass sand approaching/a predetermined analysis, from a raw material excessivek in feldspar, deficient quartz and containing iron-contaminating impurities, Which comprises; subjecting said rawvfmaterial to attrition scrubbing, Aand desliming;V conditioning Vin an acid circuit with a promoter and frother;

floating to produce a concentrate rich in iron and a tailing substantially'iron-free; effecting the removal of the feldspar content from a portion of said tailing by 'condi-v tioning said portion with hydrofluoric acid, a frother and promoter, and separating by flotation said conditioned tailing into a fraction containing ltherremoved feldspar and .a quartz fraction; and intimately mixing said quartz fraction With the remainder of said tailing to obtain said glassfsand; the part of saidtailing conditioned Vbeing selected so as to remove an amount of feldspar equal' to separation of said tailing into feldspar and quartz -fractions except by `said conditioning operation.

2. A'method according to'claim 1 in which at least some vof the Water from the feldsparfraction is'returned to the Vscrubber discharge.V Y

00 theexcess thereof in the original material, there being no r f4 Y Y Y Y Y 3.l A method of preparing a glass sand Vapproaching .a predetermined analysis, from an iron-contaminated raw..V material containing the essential constituents of said glassV sand but with f-eidspars present in an Yamount in excess of that called for in said analysis, which comprises; subjecting said raw material to attrition scrubbingV at about 80% solids; screeningand-desliming atabout 2,0% solids;` conditioning at approximatelyi% solidsrwith sulfuric acid, fuel oil, petroleum 'sulfonates' andi-pine oil; oating at about 25% solids to produce a concentraterrich in iron 'anda taiiing 'substantiallyl iron-free; etfectingarel" moval of vfeldspa froma'porti'on of said'tailing'by-conditioning said portion of said tailing at approximately solids with :hydrofluoricaciia 'frbther andpromoter; separatingsaid conditioned tailing by flotation at approximately 35%solids' finto a feldspar fraction and a quartz fraction; and intimatelymixing said quartz fraction with the remainder of said tailing to obtain said glass sand; the said-portion of =saidY tailing-conditioned beingV selected so asto `removean amount vof feldspa'r'equalto the excess thereof in the original material, t'herebeingA no separation of-'saidtailing-.into feldspar and rquartz fractions except vbyfsaid conditioning operations.

4.-'A'method of-pre'paring a-glass "sand 'analyzinglessri than 8.0% by Weight A1203 `and 'less -than`0.06% byV weight- FezQs, from a raw` materiall containing 'about' 0.15% lFez'Oa and-more than 11.0% A1203, whichrcommolecular Weightfallcylamine,r0.50 4lbf/ton kerosene, and

0.20 v-lb/'tonfpine Ioil;',rseparating;the vconditioned part `of saidtailingibyiiiotationEatapproximately 35% solids'irlto'V a feldsparflfractiomand a quartz fraction; freturning said quartzffraction=to=that part 'of :said tailing whichfwas-f notdewatered'andreturning atV least some of fthefwat'ei" from'fthev f'fel'dsparefractionbto cthe scrubber discharge; Y theV part 'of'saidtailingdewatered being selectedso asfto- Y removek `an amount of ffeldspar equal to" the excessr overI 26%"in the originaln'iateriaLI k "References `Citedin the'le-of'this patent UNITED :STATES PATENTS OTHER REFERENCES vM'ineiaindfQuarry Engineering', March 1941; pages A 69573. (Copy inlScienticLibrary() r 

1. A METHOD OF PREPARING A GLASS SAND APPROACHING A PREDETERMINED ANALYSIS, FROM A RAW MATERIAL EXCESSIVE IN FELDSPAR, DEFICIENT IN QUARTZ AND CONTAINING IRON-CONTAMINATING IMPURITIES, WHICH COMPRISES; SUBJECTING SAID RAW MATERIAL TO ATTRITION SCRUBBING, AND DESLIMING; CONDITIONING IN AN ACID CIRCUIT WITH A PROMOTER AND FROTHER; FLOATING TO PRODUCE A CONCENTRAT RICH IN IRON AND A TAILING SUBSTANTALLY IRON-FREE; EFFECTING THE REMOVAL OF THE FELDSPAR CONTENT FROM A PORTION OF SAID TAILING BY CONDITIONING SAID PORTION WITH HYDROFLUORIC ACID, A FROTHER AND PROMOTER, AND SEPARATING BY FLOTATION SAID CONDITIONED TAILING INTO A FRACTION CONTAINING THE REMOVED FELDSPAR AN A QUARTZ FRACTION; AND INTIMATELY MIXING SAID QUARTZ FRACTION WITH THE REMAINDER OF SAID TAILING TO OBTAIN SAID GLASS SAND; THE PART OF SAID TAILING CONDITIONED BEING SELECTED SO AS TO REMOVE AN AMOUNT OF FELDSPAR EQUAL TO THE EXCESS THEREOF IN THE ORIGINAL MATERIAL, THERE BEING NO 